Sensor Technology for CIP Processes

Many processes in the food industry take place in closed systems. When pipes or tanks are opened, there is a risk that the systems will be contaminated by the ingress of microorganisms. That is why the cleaning-in-place (CIP) process is used – automated cleaning in a closed process without dismantling the system. To ensure that containers and pipes are cleaned thoroughly, fixed or mobile CIP systems provide for sufficient flushing of the system with water or a basic, acidic or disinfecting cleaning medium. If additional sterilisation with steam is carried out, this is referred to as sterilisation in place (SIP).

Flexible CIP systems, as shown at Anuga FoodTec 2024, enable only the required amount of solution to be drawn from the corresponding tank. The collection tank is disconnected from the circuit and the object is cleaned by circulating the cleaning solution via the by-pass. The acids and alkalis in the CIP system circuit, as well as the rinsing water, are then fed back into the storage or stack tanks. This means that the media can be used multiple times, after the addition of a fresh cleaning agent. However, this is only possible if all the media can be completely separated from each other. Conductivity sensors play a crucial role in this phase separation. They recognise the different media in order to collect the liquids, thereby contributing to the conservation of resources.

Reliable sensors and valves are needed to ensure that cleaning does not disrupt production. You feed the individual media to the CIP system as needed. At Anuga FoodTec, technology suppliers are responding to this requirement with various valve systems and sensors that ensure a trouble-free, sustainable cleaning process. For example, Baumer offers hygienic sensors that quickly and accurately measure parameters such as flow rate, temperature, fill level and pressure. The PAC50 conductivity sensor showed its strengths in Cologne: It works reliably at temperatures of up to 140 degrees Celsius. "A value at which the wheat has long since been separated from the chaff," says Baumer product manager Martin Leupold. Experience has shown that many sensors reach their limits at just 100 degrees Celsius. And because the sensor tip is made entirely of the high-performance plastic polyether ether ketone (PEEK), it is extremely resistant to chemicals. "Its robustness allows the PAC50 to be used in CIP systems in which the sensor helps save time, energy, cleaning agents and water," says Leupold.

The example shows: The topic of resource consumption played an important role in the trade fair halls in Cologne. Particularly in the case of CIP processes, more water, energy or cleaning agents are often used than is absolutely necessary. The many production batches typical in the dairy industry, for example, mean many cleaning cycles, as pipes and tanks are hygienically cleaned before each batch. In other words, using the right technology can help realise savings. For example, with regard to cleaning effort. This is where Bürkert Fluid Control Systems' FLOWave technology excels. It uses surface acoustic waves (SAW) for inline flow rate measurement of the CIP fluids. In addition to measuring the flow rate and temperature, the sensor can determine other parameters such as mass flow rate and density, as well as detect gas bubbles and particles. This optimises the cleaning process, as the sensor can distinguish between the flushing medium and the product, reducing waste and waste-water pollution. The measuring principle requires no components that come into contact with food. This has several advantages, because no elements in the measuring tube means neither leaks nor material incompatibilities nor maintenance. In addition, there is no pressure drop in the system and cleaning is simple.

Diaphragm valves are further key components in hygienic systems. They control the flow of media during CIP cleaning. However, valves with conventional forged or cast housings consume a relatively large amount of energy – not only during production, but also during operation. SIP processes in particular require large quantities of pure steam to bring the massive valve bodies up to the sterilisation temperature. At the same time, the time during which production can take place is reduced because the housings heat up and cool down only slowly. Design details can help to further reduce the consumption of resources here.

Bürkert Fluid Control Systems offers a practical alternative with the significantly lighter 3G tube valve body. The weight reduction for a two-inch valve can be up to 75 %. The housings, manufactured using the principle of hydroforming, heat up faster and also cool down more quickly. At a temperature difference of 100 degrees Celsius, energy savings of over 50 percent can be achieved per SIP cycle. Multiplying this value by the number of CIP/SIP processes per year results in a considerable cost reduction. At the same time, the productivity of the system increases because the more efficient heating and cooling process shortens the non-productive times for cleaning. In addition, the temperature-sensitive diaphragms are subject to less thermal stress. Depending on the application, this can more than double their lifespan, which in turn extends service cycles and reduces hydrocarbon-intensive elastomer waste.

For the described savings to be realised, a high degree of transparency is required with regard to what is actually occurs in the systems. It is often difficult to see whether CIP runs are effective and efficient in an automated system. As a result, food manufacturers are trying to achieve greater process reliability through longer cleaning cycles. The danger here is: Cleaning agents are wasted and disposal and energy costs increase. Last but not least, the cleaning efficiency is also influenced by the flow rate and the shear force on the inner walls. However, as not all pipes are designed for optimal flow at every point and the range of a spraying ball is not always ideal, there are areas that are more difficult to clean. To determine and improve the overall cleaning efficiency, it is necessary to monitor the cleaning behaviour at these points.

In addition to conventional measurement methods, such as conductivity and turbidity measurement in the CIP return line, the Liquitrend QMW43 from Endress+Hauser also measures the formation of deposits. The soiling of the sensor surface is continuously monitored before, during and after the cleaning process. Cleaning status monitoring is carried out at critical points in the process and provides information about cleaning efficiency. The evaluation allows conclusions to be drawn about the type of coating, and in particular whether deposits originate from the manufactured product or from the cleaning agent. The Liquitrend QMW43 therefore helps manufacturers to determine the cause of contamination. If the sensor no longer indicates any build-up or conductivity, it can be concluded that the critical points have been successfully cleaned. This makes it possible to optimise the cleaning process according to the actual conditions in the tank or pipe, resulting in time and cost savings.